FR2579279A1 - FRICTION CLUTCH - Google Patents

Abstract

FRICTION CLUTCH FOR A MOTOR VEHICLE, INCLUDING A STEERING WHEEL 1 WITH A CLUTCH COVER 5 WHICH IS SUPPORTED A DIAPHRAGM SPRING 13 THROUGH RETAINING BOLTS 27. THESE LAST THROUGH THE DIAPHRAGM SPRING CLUTCH COVER 5 WITH AXIAL SLIDING POSSIBILITY AND, ON THE SIDE AXISALLY OPPOSED TO THE DIAPHRAGM SPRING 13, ARE FIXED ON A DISC SPRING 33 WHICH LETS AGAINST THE CLUTCH COVER 5. THE DISC SPRING 33 CARRIES THE DIFFERENT BOLTS RETAINED 27 AND CONCENTRICALLY SURROUNDES THE ROTATION AXIS 3 OF THE CLUTCH. IT ENSURES A TIGHTENING WITHOUT GAP OF THE DIAPHRAGM SPRING 13. IT IS PREFERABLY CENTER INDEPENDENTLY ON THE CLUTCH COVER 5, SO THAT THE PASSAGE HOLES 31 OF THE RETAINING BOLTS 27 CAN BE PROVIDED SUFFICIENTLY LARGE FOR THOSE N 'THERE IS NO FRICTION.

Description

- i -

  The invention relates to a friction clutch, intended in particular for

motor vehicles.

  German patent application DE-19 29 823 discloses an em-

  friction clutch for motor vehicles including the drive disc

  clutch is tightened by a diaphragm3 spring between a flywheel and a plate

  pressure plate mounted integral in rotation with the flywheel, but moved

  ble axially with respect to the latter. THE diaphragm spring presents

  te of elastic fingers oriented radially inwards, and bears at its outer periphery against the pressure plate. On a smaller diameter, the diaphragm spring is supported

  against the clutch cover by means of bolts

  outfit. These latter pass through with the possibility of axial sliding of the orifices axially aligned between them of the diaphragm spring and of the clutch cover, and their heads are pressed against the side of the

  diaphragm spring which is axially turned towards the pressure plate

  if we. On the side of the clutch cover which is axially opposite

  on the pressure plate, each retaining bolt carries a spring

  that separate which concentrically surrounds the retaining bolt and is fixed to it by means of an elastic ring. The numerous disc springs compensate for the axial play between the retaining bolts and the diaphragm spring, the clutch cover and the inserted support rings

between these pieces.

  The object of the invention is to improve a friction clutch of the aforementioned type with regard to the support of its diaphragm spring against the clutch cover, so as to facilitate assembly and to provide the friction clutch with a maximum efficiency, i.e. a minimum part of the work necessary for its actuation must be used to compensate for elastic play or to overcome losses

by friction or others.

  The friction clutch according to the invention is a so-called clutch

  "tablets", where the diaphragm spring is applied at the level of its

  outer riphery against the pressure plate, and is applied

  run the clutch cover the lonIg of a circle of unreal diameter

  N i, eu ,, by lP'iterm intermediaire de bouluri, of containment. If, -, differ, ît, ttuu- -2-

  retaining ions are fixed on a single disc of generally an-

  ring and coaxially surrounding the axis of rotation of the embraydge,

  constituted for example by a disc spring or a diaphragm spring.

  As a single disc spring is used to compensate for the play of the different retaining bolts, the prestressing forces exerted

  on these bolts are identical. This results in uni-

  shape of the diaphragm spring of the clutch, and makes it possible to better adapt the spring force and the shape of this force in the event of wear of the diaphragm spring of the clutch and the support members which cooperate with it. Reducing the number of parts of the friction clutch

  provided by the use of a single disc spring simplifies assembly.

  The retaining bolts pass through the diaphragm spring and the

  clutch circle, and can be guided radially in the ori-

  fices planned for their passage. However, it has proven to be beneficial

  that fixing the radial position of the retaining bolts with respect to

  port to the clutch cover takes place not in the holes of passage of the clutch cover, but by means of the disc spring -which bears against the clutch cover. For this purpose, centering flanges, which center the disc spring with respect to the clutch cover, can be formed by stamping or by

  bend either on the clutch cover or on the spring

  than. By sufficient dimensioning of the holes for passage of the retaining bolts in the clutch cover and if necessary in the diaphragm spring, the friction of the retaining bolts can

  be practically eliminated, hence an annihilation of the performance of the em-

  clutch. To improve clutch performance, it has also

  It has been found advantageous that the retaining bolts extend appreciably.

  parallel to the axis of rotation, and can slide parallel-

  to this axis. This can be obtained in a simple manner by means of a disk spring which is substantially plane in the tightened state, the plane of the disk extending perpendicular to the axis of rotation of the clutch. Same ern cab for spring deflection due to wear

  of the diaphragm spring of the clutch, the retaining bolts be

  place berusblemetit parallel to the axis of rotation. May. line-

  mentd det. bouluiins de i-et pitiu, on ,, axets paailèle ut éqai I ffxi * mt - 3- to be obtained in the case of conical disc springs, then fixing the retaining bolts on tongues or legs radially projecting from the springs discs. Another possibility is to provide around the fixing points of the cut-out retaining bolts which only partially surround these points.

  The disc spring can be supported inside and outside

  laughing, in the radial direction, of the circle on which the

  retaining bolts. The support radially inside the pre-

  sento the advantage of allowing the use of smaller disc springs

and therefore less expensive.

  Examples of embodiments of the invention are presented below with reference to the appended schematic drawing, in which: Figure 1 is a partial view in axial longitudinal section of a friction clutch of a motor vehicle; Figure 2 is a partial side view of the friction clutch;

  Figure 3 is a partial top view of another form of exe

  cution of the disk spring usable in the clutch according to Figure 1; Figures 4 to 7 are partial views, in section, of other embodiments of a friction clutch similar to the clutch according to Figure 1; and Figure 8 is a partial top view of the disc spring used

in the clutch according to Figure 7.

  The motor vehicle friction clutch shown in fig.

  gures 1 and 2 includes a flywheel 1 which is fixed on a crankshaft not

  shown, rotating around an axis of rotation 3, of the motor

  internal bustion of the motor vehicle. A clutch cover 5 is fixed to the flywheel 1, by bolting for example. A tray of

  pressure 7 of annu] shape is arranged axially between the cover

  clutch key 5 and the flywheel 1; the pressure plate 7 is solidified

  in rotation of the flywheel 1, but axially movable relative to

  to the latter. For this purpose, the pressure plate 7 can be assembled

  wheat on the flywheel 1 by means of tangential tongues fixed on the clutch cover 5. A clutch disc 9 is disposed axially between the flywheel 1 and the pressure plate 7, a disc whose friction linings 11 can be tightened between the flywheel 1-4_ and the pressure plate 7 by a diaphragm spring 13. The clutch disc 9 is provided with a hub 15 which can be coupled without rotation, but in axial mobility, to the primary shaft of the box of

motor vehicle speeds.

  The diaphragm spring 13 has substantially the shape of a crown 17 which is applied at its outer periphery against the pressure plate 7 and at its inner periphery against the clutch cover 5. A multiplicity of elastic fingers 19

  project from the inner periphery of the crown 17,

  only radially inward. The elastic fingers 19 are separated from each other by slots 21 which widen in orifices 23 to

  the base of the elastic fingers 21. In these orifices 23 pass, feel

  substantially parallel to the axis of rotation 3, several retaining bolts 27 arranged at a distance from each other along a circle 25, which are provided on the side of the diaphragm spring 13 turned towards

  the pressure plate 7 of heads 29. The retaining bolts 27 work

  pour holes 31 of the clutch cover 5, and, as suggested by the rivet heads 35, are all riveted on the side of the clutch cover 5 which is axially opposite the diaphragm spring 13 on

  a same disc spring 33 of annular shape, which surrounds concentric

  only the axis of rotation 3. In the example of FIGS. 1 and 2, the retaining bolts 27 are fixed at the level of the internal periphery of the disc spring 33, while the latter rests at its external periphery against a rib 37 of annular shape of the

  clutch cover 5, which coaxially surrounds the axis of rotation

  tion 3. On the side of the retaining bolts 27 which is radially op-

  placed on the axis of rotation 3, metal wire rings 39, 41 are

  arranged on the one hand axially between the heads 29 and the spring dia-

  diaphragm 13 and on the other hand axially between the diaphragm spring 13

  and the clutch cover 5, which hold the cover together

  diaphragm spring 13 with the possibility of tilting.

  In the engaged position, the diaphragm spring 13 clamps the plate

  pressure 7 against the flywheel 1 via the emitting disc

  clutch 9. In doing so, the crown 17 of the diaphragm spring 13

  puie by its outer periphery against the pressure plate 7 and - 5 by its inner periphery against the clutch cover 5, by

  through the ring 41. For disengaging, a release stop

  clutch 43, which acts on the radially inner ends of the elastic fingers 19, moves the fingers 19 in the direction of the flywheel 1, against the spring force of the crown 17. The crown 17 changes support, passing from the ring 41 to ring 39, and the ring 17 now rests, by means of the retaining bolts 27 and the disc spring 33, against the clutch cover 5. At the same time, the outer periphery of crown 17 moves away

  axially of the flywheel 1, and the clutch disc 9 is released.

  The preload of the disc spring 33 is provided sufficient so that, in all operating states, the disc spring 33 can keep the diaphragm spring 13 between the rings 39, 41 without play, that is to say so that it does not '' there is no dead stroke when switching the support force from one ring to another. During operation, the preload of the disc spring 33 changes due to the wear on the support points of the rings 39, 41 and the diaphragm spring 13 on the one hand and the wear on the rings 39 on the other hand , 41 with respectively the heads 29 and the clutch cover 5. The preload of the disc spring 33 must be chosen so as to always suffice for the assembly without play of the diaphragm spring 13, even in the event of maximum wear. In other words, the pretensioning force of the disc spring 33 must be initially oversized, in order to keep

  a sufficient value once the clamping points have worn out.

  We can act on the behavior of the spring clamping points

  diaphragm 13 by an appropriate choice of the characteristic curve

  this elastic stroke of the disc spring 33. According to a first form

  execution, the disc spring 33 can be configured so as to

  seder a spring force constantly increasing with the elastic stroke-

  tick. With such a characteristic curve, it is necessary to find a com-

  promised between the requirement to initially increase the spring force enough so that it retains a sufficient value after the clamping points are worn, and the requirement that this initial value of the spring force is not too great, because excessively high clamping forces increase the friction of the diaphragm spring 13 - 6 - at the clamping points. Excessive friction at the tightening points creates hysteresis for the clutch clutch engagement and disengagement. In the embodiment of Figures 1 and 2, the hysteresis is reduced by the fact that the disk spring 33 is applied at a point - namely the rib 37 of the clutch cover - which is closer to the outer periphery of the clutch cover 5, stiffened by the flywheel 1, that the fulcrum of the diaphragm spring 13 against the clutch cover 5 which is defined by the support ring 41. In the engaged position, the area of the cover d 'clutch 5 which is connected radially to the rib 37 towards the axis of rotation 3 is deformed, due to the preload of the diaphragm spring 13, moving away axially from the flywheel 1, to the right in FIG. 1, while the bearing area of the disc spring 33 which is formed by the rib 37 remains substantially stationary in the axial direction. In the engaged position, the axial deformation of the support area of the diaphragm spring 13 thus reduces the preload of the disc spring 33 and consequently the clamping force responsible for the hysteresis.

  -at least on part of the coupling and dice stroke-

  diaphragm spring 13 coupling. The hysteresis behavior is

  thus improved, without fear of an inadmissible reduction

  susceptible, due to wear, of the clamping force in the disengaged position.

  The diaphragm spring 13 usually has a characteristic curve.

  "raised" elastic force-stroke teristics, that is to say according to

  which spring force starts to increase with the elastic stroke-

  tick, goes through a maximum then decreases while the race continues to increase, and finally reaches a minimum and increases again, while the race always increases. It is also possible to provide a characteristic “raised” curve for the disc spring 33. In this way, the force with which the diaphragm spring 13 is clamped between the rings 39, 41 can be adapted to the modification of the prestressing force of the diaphragm spring. 13 due to wear of

  friction linings 11 of the clutch disc 9. The spring diameter

  phragme 13 and disc spring 33 are mounted with a preload according to which the spring force decreases when the elastic stroke

  increases according to the shape described above of the characteristic curve

  -7- "raised" characteristic. When the friction linings 11 wear, the preload of the diaphragm spring 13 increases accordingly, which requires an increase in the preload force of the disc spring 33 if the diaphragm spring 13 is to continue to be tightened without clearance. As the disc spring 33 also has an elevated characteristic curve, the wear of the clamping points - namely for example rings 39, 41 with the parts which bear against them - which occurs simultaneously with the wear of the friction linings 11 causes a reduction in the elastic stroke of the disc spring 33, and therefore. also an increase in the prestressing force. We know methods allowing to act on the characteristic

  of a disc spring. We can for example act on the character-

  springy by an adequate dimensioning of the ratio between the height and the thickness of the disc spring, or by giving the latter an adequate configuration, by concentric ribs or

other similar shapes.

  We will now present different embodiments of the friction clutch according to Figures 1 and 2. The parts having a

  same function keep the same reference numbers as in the fi

  gures 1 and 2, to which a letter has been added to distinguish them.

  For detailed explanations, refer to the description of

Figures 1 and 2.

  A]. In FIG. 1, the retaining bolts 27 are directly riveted on the crown of the disc spring 33. Consequently, the modification

  of] .a elastic] .astic stroke, for example due to wear of the service points

  rage of the diaphragm spring 13, causes the bolts to tilt

  retainer 27 with respect to the axis of rotation 3, and may under conditions

  unfavorable conditions influence the clutch and slackening properties

friction clutch clutch.

  Figure 3 shows a different embodiment of a disc spring 33a, where the retaining bolts are riveted on tabs 45 which project from the inner periphery of the disc spring 33a, inward in. radial. The tabs 45 allow fixing of the retaining bolts 27 which has elasticity to bending within given limits, and allow sliding movements of the retaining bolts 27 parallel to the axis of

clutch rotation.

  In FIG. 1, the disc spring 33 is centered on the clutch cover 5 by means of the retaining bolts 27. FIG.

  4 shows a different embodiment where the container cover

  clutch 5b has, in the area overlapping radially with the disc spring 33b, the shape of a cone 47. The disc spring 33b is supported

  against the radially outer part of the cone 47, and extends to dis-

  axial tance of the latter in the radially inner part. At

  rest, the disc spring 33b is arranged substantially in plan and

  pendulum to the axis of rotation of the clutch, in order to obtain a sliding substantially parallel to the axis of rotation of the clutch of the retaining bolts 27b provided for the support of the spring

  diaphragm 13b. The centering of the retaining bolts 27b on the cover

  clutch key 5b is effected via the disc spring 33b, the outer periphery 49 of which is radially centered on a

  centering collar 51. The centering collar 51 is formed by estam-

  page on the clutch cover 5b, and it should not extend beyond the entire circumference of the disc spring 33b. The centering collar 51 can also be formed by bending or by cut tabs. The holes 31b intended for the passage of the bolts

  27b in the clutch cover 5b are provided suf-

  large enough so that the retaining bolts 27b can pass through it

  smooth without friction. This increases the efficiency of the clutch.

  Unlike FIG. 4, the disc spring 33c in FIG. Is centered radially by its internal periphery on a centering collar 53 bent axially on the internal periphery of the clutch cover 5c. The retaining bolts 27c provided for tightening the diaphragm spring 13c are again centered on the clutch cover 5c by means of the disc spring 33c, the holes 33c intended for the passage of the retaining bolts 27c in the clutch cover. 5c being again provided large enough to allow sliding without friction of the retaining bolts 27c. The disc spring 33c is applied by its outer periphery - 9 - against the clutch cover 5c. Unlike FIG. 4, the clutch cover 5c is plane in the zone of overlap with the disc spring 33c, and it extends perpendicular to the axis of rotation of the clutch, while the disc spring 33c has the shape of a cone. The disc spring 33c is provided with a circular rib 53

  annular in shape, which increases its elastic force.

  FIG. 6 represents an embodiment o, in the zone o

  they overlap radially, the clutch cover 5d and the

  disc fate 33d are substantially flat and extend parallel to each other and substantially perpendicular to the axis of rotation of

  the clutch. The disc spring 33d is provided on its outer periphery

  of a support flange 55 formed by bending in the axial direction, with which it is applied against the clutch cover 5d and which keeps it at an axial distance from the latter. The disc spring 33d is provided on its inner periphery with a centering flange 57 which engages in an internal opening 59 of the clutch cover 5d and centers the disc spring 33d relative to the latter. Again,

  the retaining bolts 27d provided for tightening the diaphragm spring

  me 13d are centered on the clutch cover 5d via

  disc spring 33d. Again, the holes 31d allow the

  retaining bolts 27d to cross the friction cover without friction

clutch 5d.

  Figures 7 and 8 show details of an execution form.

  tion of a friction clutch o, unlike the forms of execution

  tion presented above, the disk spring 33e provided for tightening the diaphragm spring 13e is applied against the clutch cover e on the side of the retaining bolts 27e which is radially turned towards the axis of rotation of the clutch. This measure allows the use of smaller disc springs, and therefore a less expensive manufacture of the friction clutch. Again, the retaining bolts 27e are centered on the clutch cover 5e via the disc spring 33e; for this purpose, the clutch cover 5e is provided at its inner periphery with a centering flange 61. Again, the through holes 31e of the retaining bolts 27e in the clutch cover 5e are provided sufficiently large for

- 10 -

  allow sliding without friction of the retaining bolts 27e.

  To allow elasticity in bending (within given limits) of the fixing of the retaining bolts 27e on the disc spring 33e, the latter is provided on the side near the axis of rotation of the clutch of each retaining bolt 27e of a cutout 63 in the form of a semicircular slot, which surrounds the retaining bolts 27e and extends to the circle 25e (circle for the arrangement of the retaining bolts). In the event of wear of the tightening points, the cutouts 63 allow a tilting movement of the retaining bolts 27e relative to the disc spring 33e, and consequently a sliding which remains

substantially parallel to the axis.

  Instead of assisting the fixing of the retaining bolts 27e by the

  cutouts 63, these can also be attached to the peri

  outer spring of disc spring 33e using similar tabs

  to the legs 45 of FIG. 3. The fixing by means of legs or of

  cuts can also be used for se-

  lon FIGS. 4 to 6. With regard to the centering flanges or similar elements which have been mentioned above for the radial centering or the maintenance at axial distance of the fixing points of the retaining bolts on the disc springs, it is also possible to replace these edges or continuous supports with lugs or lugs,

or other similar items.

- 11. -

Claims (16)

  1. Friction clutch, comprising: a. a flywheel (1) rotatable about an axis of rotation (3), b) a clutch cover (5) fixed on the flywheel (1) rc) a pressure plate (7) mounted integral in rotation with the flywheel (1, but axially displaceable relative to the latter, d a clutch disc (9) disposed axially between the flywheel (1) and the pressure plate (7), ej a diaphragm spring (13) substantially in the shape of a crown , clamped between the clutch cover (5) and the pressure plate (7), and pressing at its outer periphery against the pressure plate (7), f) several retaining bolts (27) arranged radially , remote   ] es each other, inside the outer periphery of the res-   diaphragm outlet (13), on a circle (25) centered relative to the axis of rotation (3), and movable relative to the diaphragm spring (13) and the clutch cover (5), substantially in the direction of J 'axis of rotation (3). which bear at their first end against the side of the diaphragm spring (13; which is axially rotated towards the   pressure plate (7), and by their second end, via the   middle of elastic means (33, against the side of the   clutch (5) which is axially opposite the diaphragm spring (13),   characterized in that the elastic means is constituted by a res-   disc outlet (33) of annular shape acting in the axial direction and   coaxially rotating the axis of rotation (3), on which the   second ends of the different retaining bolts (27).   2. Friction clutch according to claim 1, characterized in   that the second ends of the retaining bolts (27) are banked disc spring tees (33).   3. Friction clutch according to claim 1 or 2, characterized in that the disc spring (33a - 33e) is centered radially, independently, on the clutch cover (5b - 5e), and that the retaining bolts (27b - 27e) pass through holes with radial clearance   (31b - 31e) of the clutch cover (5b - 5e).   4. Friction clutch according to claim 3, characterized in - 12 -   that a centering flange (51; 53), which guides the spring radially   disc fate (33b - 33c) on one of its peripheral edges, is formed   by stamping or bending on the clutch cover 15b; 5c).   5. Friction clutch according to claim 3, characterized in that a centering flange (57) is formed by bending on the peri-   inner spring of the disc spring (33d), rim which is radially guided   Lement against a flange (59), facing the axis of rotation, of an ori-   central part of the clutch cover (5d).   6. Friction clutch according to any one of claims 1   to 5, characterized in that a support zone (37; 47) of annular shape-   re, protruding axially towards the disc spring (33; 33b ;, is formed on the clutch cover (5; 5b), which keeps the disc spring (33; 33b) at an axial distance from the clutch cover; 5; 5b / in the vicinity of the circle (25) on which the bolts of the restraint (27; 27b).   7. Friction clutch according to claim 6, characterized in   that the support zone is formed by a rib (37), of an-   ring, clutch cover (5).   8. Friction clutch according to claim 7, characterized in that, in their mutual overlap zone, radially next to   the support zone (37), the disc spring (33) and the emitter cover   clutch '(5) extend substantially parallel to each other.   9. Friction clutch according to claim 6, characterized in   that to form the bearing area, the clutch cover (5b 're-   has a conical shape in the area (47) of radial overlap with the disc spring (33b).   10. Friction clutch according to any one of claims 1   to 5, characterized in that the disc spring (33d) carries, on its peripheral edge which bears against the clutch cover; 5d), support means (55) -which hold the disc spring (33d! axially away from the clutch cover (Sd) in the vicinity of the circle   (25) on which the retaining bolts (27d) are arranged.   11. Friction clutch according to any one of claims 1   to 10, characterized in that the disc spring (33a) carries tabs (45) extending substantially radially projecting from one of its edges - 13 -   peripheral and spaced apart from each other in the direction   circumferential, to which the retaining bolts (27a) are attached.   12. Friction clutch according to any one of claims 1   to 10, characterized in that the disc spring (33e) has a   cut (63) partially surrounding the fixing points of the plugs retention lions (27e).   13. Friction clutch according to claim 12, characterized in that the cutouts (63) are made in the form of substantially semicircular slots which surround the fixing points of the retaining bolts (27e) on the radially adjacent side of the zoned   of the disc spring (33e) against the clutch cover (5e).   14. Friction clutch according to any one of claims 1   to 13, characterized in that the disc spring (33e) is applied by   its inner periphery against the clutch cover (5e).   15. Friction clutch according to any one of claims 1   to 13, characterized in that the disc spring (33) is applied by its outer periphery against the clutch cover (5), radially outside and at a distance from a circle along which the diaphragm spring (13) is itself applied against the clutch cover (5).   16. Friction clutch according to any one of claims 1   15, characterized in that both the diaphragm spring (13) and the disc spring (33) have an elevated elastic force-stroke characteristic curve, according to which, over part of the elastic stroke, the spring force decreases when the stroke increases, and the diaphragm spring (13) and the disc spring (33) are prestressed so that changes in the stroke   elastic due to wear are located in this part of the curve typing.